This invention is an improvement in hybrid resin foam compositions such are disclosed in Brooks et al U.S. Pat. No. 5,344,852, and in the catalyst systems useful therein. The entire specification and claims of Brooks et al U.S. Pat. No. 5,344,852 are incorporated herein by reference.
The Brooks et al U.S. Pat. No. 5,344,852 describes a water blown unsaturated polyester-polyurethane hybrid resin foam formed by contacting an "A side" polyfunctional isocyanate compound and a free radical initiator, and a "B side" composition having three components--(i) an ethylenically unsaturated monomer in which a more or less conventional polyester polyol is dissolved, (ii) a polyamine compound capable of reacting with the A side composition to form dispersed, small, urea domains, and (iii) about 25 to 150 equivalents of water based on 100 equivalents of active hydrogen in the B side (not including that in the water). Further requirements are that the active NCO groups of the isocyanate should be about ten to about fifty times the number of active NH groups in the amine compound, and the isocyanate index should be between 0.5 and 2.0.
We have found that, in practice, certain properties of the various compositions which can be made by following the recipes of the '852 patent are difficult to predict or control. In particular, blistering sometimes occurs at the interface of the rigid foam and the acrylic sheet to which it is to adhere, causing (in addition to an unsightly defect which is difficult to explain) weaknesses and occasional delamination.
We have determined that it is possible to establish an association of the blistering and delamination phenomena with zones of high residual monomer. As will be demonstrated below, the incidence of blistering and delamination are greatly reduced when the monomer is almost completely polymerized in accordance with our invention. The invention involves improvements in the catalyst system.
Prior to the present invention, free radical initiators such as benzoyl peroxide (which may be referred to also as dibenzoyl peroxide) have become well known as "room temperature" initiators for polyester systems including polyester-polyurethane hybrid systems. That is, they will begin initiating a polymerization reaction in a more or less conventional unsaturated polyester polymerization mix as soon as the initiator is contacted with the polyester at temperatures as low as room temperature. Among the other well known such initiators are methyl ethyl ketone peroxide, methyl isobutyl ketone peroxide, 2,4-pentanedione peroxide, di-t-butyl peroxide, dicumyl peroxide, dilauroyl peroxide, and cumyl hydroperoxide.
Certain other initiators are known to require temperatures higher than room temperature to initiate the reaction. Such known compounds include various peroxyesters, peroxycarbonates, and peroxyketals, in particular such compounds as t-butyl peroxypivalate, t-amyl peroxybenzoate, 2,5-dimethyl-2,5-di-(2-ethylhexanoylperoxy)hexane, t-amyl peroxy-2-ethylhexanoate, t-amyl peroxyacetate, t-butyl peroxy-3,5,5-trimethylhexanoate, t-butyl peroxy-2-ethylhexyl carbonate, t-butyl peroxy isopropyl carbonate, t-butyl peroxy-2-ethylhexanoate, di(4-t-butylcyclohexyl) peroxydicarbonate, 1,1-di-(t-butylperoxy)cyclohexane, and 1,1-di(t-butylperoxy)-3,5,5-trimethylcyclohexane.
We are not aware of the use of a combination of room temperature initiators with higher temperature initiators in the combination of polyesters and isocyanates which we use nor in such a combination to provide the advantages we outline herein.